Tag Archives: science

New paper: Food supply – not ‘live fast, die young’ mentality – makes male crickets chirpy

I have a new paper out in the journal Functional Ecology, entitled ‘Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling‘. This is work from my PhD with Luc Bussière at Stirling, along with collaborators from the University of Exeter’s Cornwall campus (where I’m currently based).

We used dietary manipulations as well as manipulation of potential mate availability to investigate how male sexual signalling changes with current budget and previous expenditure. We found some cool results about what causes variation in age-dependent sexual signalling – these have implications for ‘honesty’ in sexual displays, and are also a nice reminder that there are simpler explanations than we (as humans, who love seeing patterns in the noise) often cling to.

Our paper also includes a nice example of using ‘zero-altered’ statistical models, enabling us to partition out effects on why males call from the effects on how long they call.

You can find the paper here, or email me for a PDF if you don’t have access to the journal.

Alternatively, the press office at Exeter put together a nice press release, which I’ve pasted below:


 

Shedding a few pounds might be a good strategy in the human dating game, but for crickets the opposite is true.

Well-fed male crickets make more noise and mate with more females than their hungry counterparts, according to research by the universities of Exeter and Stirling.

It has long been believed that males who acquire ample food can adopt a “live fast, die young” strategy – burning energy by calling to attract females as soon as they are able, at the expense of longevity – while rivals with poorer resource budgets take a “slow and steady” approach, enabling them to save resources and take advantage of their savings later in the season.

But the researchers found that increased diet – rather than any strategic decision by the cricket – led the best-provisioned crickets to chirp for longer. This had no noticeable cost to their lifespan.

Meanwhile hungrier males not only signalled less – meaning fewer female visitors – but also died younger.

Senior author Dr Luc Bussière, of the University of Stirling, said the findings offered a “simpler alternative” to understanding the behaviour of crickets.

“While it was intriguing to think that males might foresee and plan for their future reproductive prospects by strategically staying quiet, what our experiment suggests is actually easier to understand: rather than relying on an ability to forecast the future, crickets appear instead to respond mainly to the resources they have in hand,” he said.

Male crickets signal to females using an energetically expensive call, produced by rubbing together their hardened forewings.

The more time they spend calling, the more mates they attract.

The paper, published in Functional Ecology, studied decorated crickets, which mate about once a day on average during their month-long adult life.

Males need a three-hour recovery period following each mating to build a new sperm package, after which they are able to call again in the hopes of attracting another female.

Researchers found that a male cricket’s decision about whether to call was primarily based on whether females were nearby – rather than how well-fed they were – but the better-nourished males were able to call for longer and thus increase their mating prospects.

The study also provides insights into how energy budgets keep male displays honest for choosy females over the course of the mating season.

“In nature, a ‘better quality’ male will likely have better access to resources,” said lead author Dr Tom Houslay, a Postdoctoral Research Associate at the University of Exeter.

“Low-quality males might be able to ‘cheat’ by calling a lot one day, making females think they are high-quality, but this is not sustainable – so there is ‘honesty on average’.

“A female may be fooled once or twice, but over time males with more energy will call more – meaning females should tend to make the ‘correct’ decision by preferring those males.”

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Of carts and horses

I have been working on a post for some time now, in which I was planning to use web-scraping in R to gather sports-related data from webpages and then run some fancy analysis on it. But when I say ‘working on’, I mean that I’ve playing around with the data, staring at a whole bunch of exploratory plots, and trying to come up with an angle for the analysis.

And, so far, I’ve come up with: nothing.

But perhaps some good can come out of this. The process of trying to come up with an idea to fit the data reminded me of this quote by Sir Ronald Fisher (I should admit that I know of the quote because a guy on the R mixed models mailing list has it in his signature):

To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.

In the past couple of years, I’ve started teaching week-long statistics workshops (*cough*), which are incredibly satisfying (if also incredibly draining!). I have also gone through that enlightening period where learning a little more makes you realise how much you don’t know, which opened up a whole slew of new things to learn (also, I have started listening to statistics-related podcasts, which possibly means that I need professional help). I’m lucky in that I’ve managed to figure out some of this stuff, which leads to other people now coming to me for help with their analysis. Questions range from ‘does my model look ok?’ all the way to ‘I have this data, how should I analyse it?’. The latter always brings that quote into sharper focus.

It’s for this reason, the idea that statistical analysis should be an intrinsic part of the planning of any project, that I was interested to read articles recently on the idea of registering studies with journals prior to gathering the data. This idea stems mainly from the fact that too much of whether something gets published depends on it being a positive result, and the ‘spin’ of the results – with hypotheses often dreamed up post-hoc – affects which journal the study gets published in (obviously there’s more nuance than that, but maybe not that much more). By registering the design beforehand, you can go to a journal and say: this is the question, here are our hypotheses, here’s how we’re going to tackle it with an experiment, and here’s how we will analyse the data. The journal would then decide beforehand if they think that’s worth publishing – whatever the result.

This is a little simplistic, of course – there would have to be the usual review process, and there would obviously be leeway for further analysis of interesting trends on a post-hoc basis – but it would enforce greater thinking about an analysis strategy prior to embarking on a study. Even the simple task of drawing out the potential figures that would come out of the data collection is crucial to the process, as they help to clarify what is actually being tested.

So – that post I was originally setting out to write? I have the data, but I still haven’t had any good ideas for how to use it. And maybe it’s that kind of backwards approach that we all need to stay away from.

Further reading:

Nature: ‘Registered clinical trials make positive findings vanish

Kaplan & Irvin (2015) Plos One: ‘Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time

The Guardian: ‘Trust in science would be improved by study pre-registration

The Washington Post: ‘How to make scientific research more trustworthy

New York Times: ‘To get more out of science, show the rejected research

FiveThirtyEight: ‘Science isn’t broken‘ (This is a must-read)

My favourite statistics podcasts!

Not so standard deviations

FiveThirtyEight’s ‘What’s the point?’

Breaking Bio: the new podcast for AWESOME COOL PEOPLE and also YOU

Recently, I have joined with some colleagues from around the world in a new venture which combines several things that I feel rather passionately about: science communication, trying to get over my crippling self-confidence / public speaking issues, and generally chatting shit about insect humping. That’s right, there’s a new podcast in town! It’s called Breaking Bio, and it all stemmed from the mind of Steven Hamblin, the guy who shot to fame after taking various reporters and commentators to task in the ‘dolphin rape edition‘ of his blog. Here he is in all of his glory:

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I should probably mention that the blog post in question was actually a rather sober discussion of science journalism and sensationalism in the mainstream media, but hopefully the previous paragraph and accompanying picture will have done the desired damage to Steven’s reputation.

The podcast itself is a light-hearted chat between a bunch of nerds about various topics: recent discoveries, big topics in the scientific community, conferences, weird insect genitalia…   all of the things you’d expect, and maybe more (especially when Bug Girl is around!)

We are about 6 episodes in just now, so there’s plenty for you to catch up on – there’s also something of a rotating cast of characters to get acquainted with:

Steven Hamblin – yeah, the dolphin rape guy in the underpants. Not only does Steven have to try and figure out times for various people across the globe to chat for an hour or so once a week, he also has the job of keeping us on a vague topic, and the frankly horrendous task of editing it all into something coherent afterwards. Oh, and he’s a postdoc in Australia doing extremely hard maths about zombie caterpillars.

Morgan Jackson – entomology PhD student at Guelph, awesome photographer, and fly lover. But not like Steven is a dolphin lover. This is a purer love.

Rafael Maia – a PhD student at the University of Akron, Rafael does some unbelievably cool work on the evolution of bird feather colouration. He’s also, like, Mexican or something. I dunno.

Bug Girl – with a PhD in entomology and a reluctance to reveal her true name, Bug Girl is something of an enigma. She’s like a superhero, albeit one whose superpower is talking non-stop about insect genitalia and how Spiderman should really spooge web out of his butt and suchlike. Basically, she’s fucking brilliant.

Crystal Ernst – another entomology PhD student and awesome photographer, Crystal also blogs as ‘The Bug Geek’, no doubt invoking her own ire as she struggles to contain her geekiness solely to the order Hemiptera.

Michael Hawkes – unfortunately, Michael is doing a PhD in something which can be described as ‘applied’, seeing as it might be of practical use one day, so I’ll be damned if I’m going to lower myself to writing about it here. He’s at the University of Exeter. He also MAKES ME SICK.

We’re also hoping to extend this list to a few more characters, with hyper-enthusiastic science goblin Lauren Reid lined up to join us in future, the fabulous Bug Chicks stopping by, and PROPER GROWN-UP REAL SCIENTIST GUY Rob Brooks having been cajoled into making a guest appearance. Rob shall likely be discussing his book, ‘Sex, Genes, and Rock & Roll‘. Hopefully we can also get him to respond to what is probably my favourite ever online comment, left underneath his article on cats and toxoplasmosis:

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…but perhaps his cameo appearance on the podcast will make him feel better? Either that, or we’ll send him spiralling further down into a pit of despair.

But where can I watch this awesome sounding podcast?, you may be wailing at this point, anguished by my inability to write a short blog post that gets to the point within a reasonable number of characters, why dost thou maketh me wait like some putrid syphilis-riddled chump, you cry, suddenly resorting to ye olde English like creationists do when you’ve argued them down and they’re trying to regain the upper hand through patronising misquotations of not-particularly-relevant bible verses.

WELL

Subscribe via iTunes

Watch the videos on YouTube

Follow @BreakingBio on Twitter for updates